Curve Patterns in Chiari I Malformation and/or Syringomyelia

Purpose: Patients with presumed idiopathic scoliosis may have an underlying neurologic diagnosis despite a normal history and physical exam. This retrospective radiographic review analyzes curve patterns in patients with scoliosis associated with a Chiari I malformation and/or syringomyelia. Our goal was to better define the “atypical curve” and to potentially refine the indications for further imaging.

Method: PA and lateral radiographs were reviewed in 41 patients with Chiari I and/or syringomyelia, focusing on curve pattern, apex, levels, balance, thoracic kyphosis, and lumbar lordosis. “Common” patterns, as defined by historic controls, were used for comparison.

Results: The mean age was 12 years (4-19 yrs), and 44% were male. Single thoracic curves were found in 51%, and 32% of major curves were left sided. Nine patterns were identified: R Thor (32%), R Thor/L Lum (17%), R Thor/L TL (5%), L Thor (20%), L Thor/R Lum (5%), L Thor/R TL (2%), Double Thor (10%), triple curve (5%), and L TL (5%). 46% had an uncommon curve pattern, and 73% of common curve patterns had atypical features. In single right thoracic curves (13), the UEV was T1-T4 in 4 and T7 in 3, with a LEV from L1-L3 in 12 (apex T10-T11 in 10, 8.8 levels avg.). The typical “idiopathic” curve from T5/6 to T11/12 was not seen. In the R Thor/L Lum curves (7), the thoracic UEV was T1-T4 in 4, and the lumbar UEV was T9/T10 in 3. The mean thoracic kyphosis (T3-T12) was 41° (19-70), and kyphosis across the involved segments in thoracic curves was 27.5° (-5 to 64). Lumbar lordosis was 60° (22°-90°).

Conclusion: In addition to a higher percentage of male patients, scoliosis in this population may be characterized by 1.) uncommon patterns: left sided curves, triple curves, and certain double major curves (reverse double thoracic, left thoracic/ right lumbar, thoracic with thoracolumbar); 2.) a superior or inferior shift of one or both end vertebrae in some curves with common patterns (R Thor, R Thor/L Lum), 3.) preservation or accentuation of thoracic kyphosis (T3-T12). A heightened index of suspicion may be warranted if one or more of these findings is present.